Create importer script for Cloudflare public IP ranges

[fershad]

Is your feature request related to a problem? Please describe.
Currently, information about Cloudflare's IP ranges needs to be manually maintained. This can lead to it being out of date fairly quickly.

Describe the solution you'd like
Cloudflare publishes a list of public IP ranges (IPv4 and v6) which it regularly updates and maintains. The ideal solution would be to create an importer script like the ones present for Google, AWS, Microsoft, and Equinix (https://github.com/thegreenwebfoundation/admin-portal/tree/master/apps/greencheck/importers). This can then be used to automate the updating of Cloudflare IP ranges.

List of public IP ranges: https://www.cloudflare.com/ips/
TXT IPv4 list: https://www.cloudflare.com/ips-v4/#
TXT IPv6 list: https://www.cloudflare.com/ips-v6/#

Information can also be accessed via the Cloudflare API as outlined in these docs: https://developers.cloudflare.com/api/operations/cloudflare-i-ps-cloudflare-ip-details

[fershad]

Before getting started on this, it would be super handy to find someone at Cloudflare who can confirm that these are the only IP ranges they use for customers. If others do exist, then it'd be useful to know where we can find those too so that they can also be included in this update.